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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 9 |
| 3 | 70 |
| 4 | 535 |
| 5 | 3906 |
| 6 | 29274 |
| 7 | 215900 |
| 8 | 1628175 |
| 9 | 12197570 |
| 10 | 92830430 |
| 11 | 704127060 |
| 12 | 5400199350 |
| 13 | 41331491124 |
| 14 | 318871044756 |
| 15 | 2456608834680 |
| 16 | 19039140186495 |
| 17 | 147401590706370 |
| 18 | 1146463189301430 |
| 19 | 8909683732878500 |
| 20 | 69495629981713650 |
[1,9,70,535,3906,29274,215900,1628175,12197570, 92830430,704127060,5400199350,41331491124, 318871044756,2456608834680,19039140186495, 147401590706370,1146463189301430,8909683732878500, 69495629981713650] |